JSFiddle - React, Tailwind, and code Playground

HTML

<form>
	<span class="timer-title"><strong>Activity timer</strong></span>h: <input id="hours" readonly="readonly" size="2" type="text" />&nbsp;m: <input id="minutes" readonly="readonly" size="2" type="text" />&nbsp;s: <input id="seconds" readonly="readonly" size="2" type="text" /><span class="timer-buttons"><input onclick="doTimer()" type="button" value="Start" /> <input onclick="stopCount()" type="button" value="Stop" /> <input onclick="resetCount()" type="button" value="Reset" /> </span></form>

JavaScript

var sec=00;
var min=00;
var hr=00;
var t;
var timer_is_on=0;

function timedCount()
{

  if (min==0) {
   min=1;
  }
  document.getElementById('seconds').value=sec;

  document.getElementById('minutes').value=min;
  $('.node-form .form-item:nth-child(4) input').val(min);

  document.getElementById('hours').value=hr;
  $('.node-form .form-item:nth-child(3) input').val(hr);

  sec=sec+1;
  if (sec==60)
  {
    sec=0;
    min=min+1;
    if (min==60)
    {
      min=1;
      hr=hr+1;
    }
  }
  t=setTimeout("timedCount()",1000);
}

function doTimer()
{
  if (!timer_is_on)
  {
    timer_is_on=1;
    timedCount();
  }
}

function stopCount()
{
  clearTimeout(t);
  timer_is_on=0;
}

function resetCount()
{
  stopCount();
  sec=0;
  min=0;
  hr=0;
  document.getElementById('hours').value=00;
  $('.node-form .form-item:nth-child(3) input').val('0');
  document.getElementById('minutes').value=00;
  $('.node-form .form-item:nth-child(4) input').val('0');
  document.getElementById('seconds').value=00;
}

function putInTimelog()
{
  // Put hours
  var hourItems=[];
  var hourFields=document.getElementById("node-form").getElementsByTagName("input");
  for (var i=0; i<hourFields.length; i++) {
    //omitting undefined null check for brevity
    if (hourFields[i].id.lastIndexOf("edit-field-timelog-hours-0-value-", 0) === 0) {
      hourItems.push(hourFields[i]);
    }
  }
  var hourField='edit-field-timelog-hours-0-value-';
  hourField=hourField.concat(hourItems.length);
  document.getElementById(hourField).value=hr;
  // Put minutes
  var minuteItems=[];
  var hourFields=document.getElementById("node-form").getElementsByTagName("input");
  for (var i=0; i<hourFields.length; i++) {
    //omitting undefined null check for brevity
    if (hourFields[i].id.lastIndexOf("edit-field-timelog-minutes-0-value-", 0) === 0) {
      minuteItems.push(hourFields[i]);
    }
  }
  var minuteField='edit-field-timelog-minutes-0-value-';
  minuteField=minuteField.concat(minuteItems.length);
 ...